Japanese Submarine I-13 History and Facts

The Japanese submarine I-13 has a rich history that spans over 70 years. It was a Type A Kōryū-class midget submarine that played a significant role in the early years of World War II.

Commissioned in 1941, I-13 was designed for covert operations and was equipped with a crew of six. Its primary mission was to conduct reconnaissance and launch surprise attacks on enemy ships.

One of its most notable features was its compact size, measuring only 22.7 meters in length and 3.8 meters in width. Despite its small size, I-13 was capable of carrying a significant payload of explosives and torpedoes.

The Japanese Submarine I-13 is a versatile vessel with a range of upgrade options. It has three gear slots, allowing for the equipping of submarine torpedoes, seaplanes, and augmentation items like Kunai and Dagger.

The I-13's efficiency increases with each upgrade, with the first slot offering a 5% boost to torpedo efficiency and the second slot providing a 10% boost. The third slot is reserved for seaplanes, which offer a 150% boost to efficiency.

Here's a breakdown of the I-13's gear slots:

The I-13 also has three limit break ranks, each offering unique upgrades and bonuses. The first rank grants All Out Assault I and a 5% boost to torpedo efficiency, while the second rank adds a torpedo mount, seaplane, and hunting radius increase. The third rank upgrades All Out Assault I to II and provides a 10% boost to torpedo efficiency.

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January–June 1945 was a pivotal period for I-13, and it's a fascinating time to explore.

I-13 was formally commissioned and attached to the Sasebo Naval District, where she was assigned to Submarine Division 1 in the 6th Fleet.

The submarine departed Kobe for Kure, Japan, after her commissioning, and arrived at Kure on 17 December 1944, marking the beginning of her operational journey.

I-13 conducted work-ups and combat training with other submarines in the western Seto Inland Sea during January 1945, honing her skills and preparing for future missions.

The submarine also served as an antisubmarine warfare target for Japanese destroyers Kamikaze and Nokaze on 19 January 1945, providing valuable training for their crews.

The United States Army Air Forces conducted a major fire-bombing raid on Tokyo on the night of 9–10 March 1945, prompting the 6th Fleet to propose a retaliatory raid on San Francisco, California, which was ultimately rejected by the Imperial Japanese Navy General Staff.

I-13 managed to escape damage during the United States Navy's Task Force 58 carrier aircraft strike against the Kure Naval Arsenal on 19 March 1945, successfully submerging during the attack.

By late May 1945, I-13 and the other submarines of Submarine Division 1 had been fitted with submarine snorkels, a crucial upgrade for their operations.

I-13 and I-14 departed Kure on 27 May 1945, making their way to Moji on the coast of Kyushu, where they dropped anchor and spent the night before continuing their journey.

Operation Hikari was a Japanese reconnaissance mission in late July 1945.

I-13 and I-14 were tasked with transporting disassembled Nakajima C6N1 Saiun reconnaissance aircraft to Truk Atoll in the Caroline Islands.

These aircraft were to be reassembled at Truk and then conduct a reconnaissance of Ulithi, noting the presence and location of Allied aircraft carriers and troop transports.

The C6N aircraft were to use the reconnaissance information to assist six M6A1 floatplanes in targeting Allied ships.

I-13 loaded two crated C6N aircraft at Ōminato on the northern tip of Honshu.

I-13 departed Ōminato on 11 July 1945 to begin Operation Hikari, heading for Truk, where she was scheduled to arrive on 20 July 1945.

Fleet Radio Unit, Melbourne (FRUMEL), an Allied signals intelligence unit, decrypted a message from I-13 which gave her intended approximate positions for 12:00 on 13, 15, and 18 July.

FRUMEL personnel incorrectly assessed that Operation Hikari involved the transportation of approximately four suicide attack aircraft to Singapore.

The Japanese never heard from I-13 again after her departure from Ōminato.

The Japanese submarine I-13 was a significant vessel in its time. It measured 82.5 meters in length.

The submarine's design was influenced by the Japanese Navy's need for a long-range submersible. Its crew consisted of 60 people.

The I-13 had a single propeller and a top speed of 19.5 knots when surfaced.

The boats in question were a series of submarines, with seven units ordered but only two completed. These submarines were part of a larger project, but unfortunately, not all of them were finished.

Two of the submarines, I-13 and I-14, had different fates. I-13 was sunk on 16 July 1945 by a combination of destroyer escort and aircraft action. I-14, on the other hand, surrendered at sea and was later scuttled off Oahu in 1946.

The remaining submarines didn't fare as well. I-15 was converted to a tanker submarine in June 1945, but was scrapped soon after. I-1 was 70% complete when it was sunk by a typhoon on 18 September 1945, and was later salvaged and scrapped.

The other three submarines, No.5094, No.5095, and No.5096, were cancelled in 1943 before they even started construction.

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The Type AM2/A3 submarines were a modified version of the original A2 type, designed to carry a second aircraft. They had hangar space for two aircraft, with the seaplanes being the Aichi M6A1 bomber, capable of carrying 800kg bombs.

These submarines were incredibly long-range, with a remarkable 21,000nmi (39,000km; 24,000mi) at 16 knots (30km/h; 18mph), but their underwater performance was compromised, making them vulnerable targets.

The class includes the smallest of the Japanese submarines, from midget submarines to manned torpedoes often used for suicide attacks.

Here are some key facts about the Type AM2/A3 submarines: